He had also been bound with tape, slashed on his back and continuously punched and kicked, said Greater Manchester Police.

Eventually after several hours the teenager was allowed to leave the house in the Werneth area on October 5 last year having suffered terrible injuries.

Three of his assailants, Shohaib Khan, 17, of Grange Avenue, Oldham; Adam Hussain, 16, of Olivers Court, Oldham, and Sufyan Yakub, 16, of Park Road, Oldham, all pleaded guilty at an earlier hearing to blackmail, false imprisonment, wounding with intent and assault.

Khan was locked up at Manchester Minshull Street Crown Court for six years and six months, while Hussain and Yakub received sentences of four years each.

A 17-year-old boy pleaded guilty to a section 47 assault and was sentenced to a 12-month supervision programme with a night-time curfew, said police.

Ahsan Khan, 15, of Cornwall Street, Oldham, received a five-year custodial sentence after he was convicted after trial of blackmail, false imprisonment, wounding with intent, assault, theft and causing a person to engage in sexual activity without consent.

Following sentencing, Detective Inspector Paul Walker said: "This was a sickening and prolonged attack on a young boy which left him so shaken and terrified that he didn't even want to tell his parents what had happened.

"The emotional scars from this shocking attack will haunt him for the rest of his life and I could not even begin to imagine the agony and suffering that he endured.

"Thankfully, his attackers have now been sentenced but this can never fully repair the damage that this barbaric incident has done.

"I want to pay tribute to the victim and his family for having the bravery to come forward and give evidence that has helped us catch and convict the people that have inflicted this upon him."